Nishizawa et al., Journal of Medicinal Chemistry, 20(4):510 (1977) have synthesized, and studied the activity of [(2S,3R)-3-amino-2-hydroxy-4-phenylbutanoyl]-L-leucine (bestatin) and analogs. Bestatin has the structural formula ##STR2## Many analogs of bestatin are reported in the reference. Among the analogs disclosed is the compound wherein L-alanine is substituted for the L-leucine moiety of bestatin. Bestatin is disclosed to be an inhibitor of aminopeptidase B and leucine aminopeptidase.
U.S. Pat. No. 3,832,337, issued Aug. 27, 1974 deals with peptides and acylated peptides that inhibit the conversion of angiotensin I into angiotensin II.
Recently many compounds falling into the general category of mercaptoacylamino acids have been found to be useful as inhibitors of angiotensin converting enzyme. The most well known of these compounds, captopril (D-(3-mercapto-2-methyl-1-oxopropyl)-L-proline) is currently being developed as a treatment for hypertension. Captopril is disclosed in U.S. Pat. No. 4,105,776.
U.S. Pat. No. 4,191,753 discloses peptides having the sequence EQU &lt;Glu-Trp-A.sub.3 -Arg-A.sub.5 -Gln-Ile-A.sub.8 -A.sub.9
wherein A.sub.3, A.sub.5, A.sub.8 and A.sub.9 each is L-proline or L-3,4-dihydroproline. The peptides are angiotensin converting enzyme inhibitors.
Dipeptides having the formula ##STR3## have also been disclosed as useful inhibitors of angiotensin converting enzyme; Patchett et al., 17th National Medicinal Chemistry Symposium, June 15-19, 1980, Troy, New York. The compound of the above formula wherein R is ethyl is currently being developed as a treatment for hypertension.